The present invention relates to the preparation of brominated aromatic compounds. More specifically, it relates to ring brominated hydroxyaromatic compounds.
It is known to prepare brominated alkyl phenols. See, e.g., Can. J. Chem., Volume 61, pages 1045-1052 (1983); and Russian Chemical Reviews, Volume 32, pages 75-93 (1963). Brominated tetraalkylhydroxyaromatic compounds having 2 aromatic rings also have been prepared in the past. Brominated tetraalkyl biphenols having the benzene rings directly linked have been prepared from tetraalkyl diphenoquinones; see, e.g. U.S. Pat. Nos. 3,929,908; 3,956,403 and 4,058,570. However, when brominating compounds wherein the aromatic rings have an alkylene bridge, the products typically do not have bromine on the aromatic rings. For example, Bradley and Sanders, J. Chem. Soc., Volume 1962, pages 480-486 (1962) disclose the reaction of 3,3',5,5'-tetra-t-butylstilbenequinone with HBr to yield .alpha.,.beta.-dibromo-4,4'-dihydroxy-3,3',5,5'-tetra-t-butyldibenzyl. Kharasch and Joshi, J. Org. Chem., Volume 22, pages 1435-1438 (1957) disclose the reaction of bromine with 4,4'-methylenebis(2,6-ditertiarybutylphenol) in the presence of acetic acid to give 1-bromo-1,1-bis-(3,5-ditertiarybutyl-4-hydroxyphenyl)methane.
The compound 2,2'-(1,2-ethanediyl)bis(3,5-dibromo-4,6-dimethylphenol) has been prepared by the hydrogenation of 4',5,6',7-tetrabromo-3',5',6,8-tetramethyl-3,4-dihydrospiro(2H-1-benzopyra n-2,1'-[3,5]cyclohexadien)-2'-one; Ann., Volume 548, pages 48-77 at page 57 (1939); and by the bromination of 2,2'-(1,2-ethanediyl)bis(4,6-dimethylphenol).
In view of the deficiencies of prior art bromination methods, it would be desirable to have a simple method for the preparation of novel ring brominated polymethylene-bridged di(dialkylhydroxyaromatic) compounds having terminal para hydroxyl moieties.